1. Field of the Invention
This invention relates to crushing and grinding friable material and to classifying the crushed material into ranges of particle size. More specifically, the present invention involves method and apparatus by which particles of friable material are efficiently crushed by grinder apparatus maintaining substantial conformance with a grinding face, and by which fluid flow velocities are controlled to determine the extent of crushing which takes plce and to calssify the crushed particles according to weight or size.
2. Brief Description of Prior Art
Numerous arrangements for crushing, mixing, kneading or otherwise acting on various types of materials, including friable materials, are known in the art. Such arrangements have proved useful in various applications, including ore processing and paint, food and drug manufacturing. However, such prior art arrangements possess certain recognized disadvantages, and these disadvantages have persisted and not been materially minimized or eliminated prior to the present invention.
One prior art disadvantage relates to efficiency. In many prior art devices an excessive amount of input energy is expended in the needless moving about of the material to be ground without actually grinding that material. Also some prior art designs needlessly overgrind the material. Among other things, reduced efficiency results in increased requirements for input energy to obtain given quantities of useable work product.
Another significant disadvantage of prior art arrangements is the inability to effectively control the amount of grinding or crushing which takes place. Although some prior art arrangements have been suggested, these arrangements generally lack the precise control to effectively remove the crushed particles from the grinding surfaces once the crushed particles have been reduced to a size or weight within a predetermined and desired range.
A further disadvantage of many prior art material processing systems involving grinding or crushing is that the crushed material must be separated or classified separately in a distinct operation from the grinding operation. Consequently separate machinery for this purpose must be provided, and its operation requires further energy consumption and supervision. Furthermore by ineffectively controlling the amount of grinding which occurs in the grinding apparatus, the material supplied for separate classification may be overground or not sufficiently crushed to the desired range of weights or sizes. In such circumstances, the material which has been crushed too finely may be unusable, or the material which has not been sufficiently crushed must be returned to the grinder apparatus.
Other disadvantages and limitations of prior art are known. Those skilled in the art may recognize other limitations and disadvantages, in view of the desirable aspects of the present invention, but comprehension of the desirable aspects of this invention should not diminish the significance of many of the previous troublesome limitations of the prior art.